Toriel

(name might change.)

In-slaved in childhood and later was brought to serve in special army forces for magical creatures, he showed a lot of talent in his combat skill and was allowed as one of very unique exception to be a personal guard to the Emperor's first born after proving his loyalty to the throne.
He protected and trained the prince as well as some of the knights and guards for the castle defences.

Later on escapes with the Prince Theodric and helps him with the resistance movement never leaving his side.